The natural diet of the Notonectidae: field trials using electrophoresis

ABSTRACT.

• 1 Field trials were conducted on populations of two sympatic species of the waterbug Notonecta (Hemiptera: Heteroptera), to examine their natural diet using the electrophoretic method of gut contents analysis.
• 2 Fingerprint esterase bands were identified from thirty-three potential aquatic prey types; gut contents of different instars of both species of Notonecta from the field were analysed.
• 3 The level of prey identification possible ranged from 73% in fifth instar N.glauca L. to 100% in third instar N.viridis Delcourt.
• 4 Type A errors, where no prey remains were detected from a full gut, were found in only 3% of the specimens analysed.
• 5 Data on gut states, the number of prey types per gut and details of aquatic prey found in the diet of different instars of field-collected Notonecta are presented.
• 6 These results are compared with previous data on notonectid diets, and the relative merits of different methods of diet analysis are discussed.

     

Multiple intraguild predators reduce mortality risk of a mutual agricultural pest prey in simple,but not in complex,experimental settings

Multiple predator species that coexist with each other and their mutual prey can have combined effects on prey mortality that are similar to the sum of each predator's individual impact (linear effects), greater than the sum of each predator's individual impact (risk enhancement), or less than the sum of each predator's individual impact (risk reduction). Understanding multiple predator effects is important to determine the impact of predators on pest prey in agroecosystems. If two predators share the same broad spatial domain and hunting mode and engage in intraguild predation, then their combination is expected to result in risk reduction for a mutual prey. We tested this hypothesis using both additive and replacement experimental designs on two species of generalist wolf spider predators (Tasmanicosa leuckartii and Hogna crispipes) that hunt in the same domain, and a mutual insect prey (cotton bollworm Helicoverpa armigera). We used two types of enclosures: a small simple laboratory enclosure, and a larger more complex cotton plant enclosure. We found that in the small simple laboratory enclosures, the presence of two spiders led to risk reduction of Helicoverpa larva mortality as expected, but in larger more complex cotton plant enclosures the presence of both species resulted in linear effects rather than risk reduction on Helicoverpa mortality. Furthermore, intraguild predation did not change multiple predator effects in laboratory or plant enclosures. This study has implications for managing arthropod predators in agroecosystems; contrary to predictions of ecological frameworks, coexistence of predators that share the same hunting mode and hunting domain may not lead to risk reduction on a mutual prey in more complex environments, where encounters among predators can be lower. Conservation of multiple predators of a single guild can play an essential role on biological control of insect pests.     

Oviposition habitat selection in response to risk of predation in temporary pools: mode of detection and consistency across experimental venue

Natural selection should favor females that avoid ovipositing where risk of predation is high for their progeny. Despite the large consequences of such oviposition behavior for individual fitness, population dynamics, and community structure, relatively few studies have tested for this behavior. Moreover, these studies have rarely assessed the mode of detection of predators, compared responses in prey species that vary in vulnerability to predators, or tested for the behavior in natural habitats. In an outdoor artificial pool experiment, we tested the oviposition responses of two dipteran species, Culiseta longiareolata (mosquito) and Chironomus riparius (midge), to the hemipteran predator, Notonecta maculata. Both dipteran species have similar life history characteristics, but Culiseta longiareolata larvae are highly vulnerable to predation by Notonecta, while Chironomus riparius larvae are not. As their vulnerabilities would suggest, Culiseta longiareolata, but not Chironomus riparius, strongly avoided ovipositing in pools containing Notonecta. An experiment in natural rock pools assessing oviposition by Culiseta longiareolata in response to Notonecta maculata yielded an oviposition pattern highly consistent with that of the artificial pool experiment. We also demonstrated that the cue for oviposition avoidance by Culiseta longiareolata was a predator-released chemical: Notonecta water (without Notonecta replenishment) repelled oviposition for 8 days. Oviposition avoidance and mode of detection of the predator have important implications for how to assess the true impact of predators and for the use of commercially produced kairomones for mosquito control.     

Effects of Chemical Cues on Foraging in Damselfly Larvae, <Emphasis Type="Italic">Enallagma antennatum</Emphasis>

Animals experiencing a trade-off between predation risk and resource acquisition must accurately predict ambient levels of predation risk to maximize fitness. We measure this trade-off explicitly in larvae of the damselfly Enallagma antennatum, comparing consumption rates in the presence of chemical cues from predators and injured prey. Damselflies distinguished among types of chemical cues based on species of prey injured or eaten. Injured coexisting heterospecific and unknown heterospecific chemical cues did not reduce foraging relative to starved predator cues, while cues arising from predators eating a coexisting heterospecific did decrease foraging. This study shows a cost in terms of reduced foraging in response to chemical cues and further defines the ability of prey to respond discerningly to chemical cues.     

Tracking predator density dependence and subterranean predation by carabid larvae on slugs using monoclonal antibodies

1. Subterranean carabid larvae are more numerous than surface‐active adults, yet very little is known about their ecological significance, dietary preferences or ability to regulate populations of prey species, particularly pests. Part of the reason for this is that predator–prey interactions beneath the soil are almost impossible to observe. 2. Extensive field studies have shown that adult Pterostichus melanarius (Illiger) can affect the temporal and spatial dynamics of their slug prey. However, if larvae too are feeding on slugs, this could radically affect overall predator–prey dynamics. 3. We tested the hypotheses that P. melanarius larvae would kill and consume two slug species, Deroceras reticulatum Müller and Arion intermedius Normand, under laboratory and semi‐field conditions, and that there would be no significant difference in rates of predation on these slug species. 4. A new monoclonal antibody was developed that was capable of detecting the presence of slug proteins in the guts of P. melanarius larvae. 5. Pterostichus melanarius larvae killed both A. intermedius and D. reticulatum in the laboratory, feeding to a greater extent, and growing more rapidly, on the latter. The larvae were equally effective at reducing numbers of both slug species in a crop of wheat grown in semi‐field mini plots, but predation was affected by density‐dependent intra‐specific competition amongst the beetle larvae. 6. Future modelling of the dynamic interactions between carabids and slugs will need to take into account predation by larvae.     

Locomotory efficiency in the predation strategies of the British Notonecta (Hempitera,Heteroptera)

Summary Locomotory efficiency and potential has been studied in three species of the waterboatman Notonecta in relation to the predation strategies of these bugs.Morphometric analysis, estimating likely relative drag forces, mechanical advantages of the swimming legs and leg length/body length ratios allowed an estimation of locomotory efficiency of the three bugs on the basis of their structural features.A study of the effect of activity on the respiration rate investigated how the predators locomotory abilities were reflected in their physiology.Finally, the relative locomotory abilities of the three predators were compared behaviourly be examining pursuit and attack success after free swimming prey in simple and complex environments.Differences were found between the three predator species which were consistent for the three experimental methods and these were successfully related to the predation strategies and habitat selection of the bugs.     

Does a top predator reduce the predatory impact of an invasive mesopredator on an endangered rodent?

The mesopredator release hypothesis (MRH) predicts that reduced abundance of top‐order predators results in an increase in the abundance of smaller predators (mesopredators) due to a reduction in intra‐guild predation and competition. The irruption of mesopredators that follows the removal of top‐order predators can have detrimental impacts on the prey of the mesopredators. Here we investigated the mechanisms via which the presence of a top‐order predator can benefit prey species. We tested predictions made according to the MRH and foraging theory by contrasting the abundances of an invasive mesopredator (red fox Vulpes vulpes) and an endangered prey species (dusky hopping mouse Notomys fuscus), predator diets, and N. fuscus foraging behaviour in the presence and absence of a top‐predator (dingo Canis lupus dingo). As predicted by the MRH, foxes were more abundant where dingoes were absent. Dietary overlap between sympatric dingoes and foxes was extensive, and fox was recorded in 1 dingo scat possibly indicating intra‐guild predation. Notomys fuscus were more likely to occur in fox scats than dingo scats and as predicted by the MRH N. fuscus were less abundant in the absence of dingoes. The population increase of N. fuscus following rainfall was dampened in the absence of dingoes suggesting that mesopredator release can attenuate bottom‐up effects, although it remains conceivable that differences in grazing regimes associated with dingo exclusion could have also influenced N. fuscus abundance. Notomys fuscus exhibited lower giving‐up densities in the presence of dingoes, consistent with the prediction that their perceived risk of predation would be lower and foraging efficiency greater in the presence of a top‐predator. Our results suggest that mesopredator suppression by a top predator can create a safer environment for prey species where the frequency of fatal encounters between predators and prey is reduced and the non‐consumptive effects of predators are lower.     

Experimental assessment of predation risk for juvenile green sturgeon,Acipenser medirostris,by two predatory fishes

Predation is a common cause of early life stage mortality in fishes, with reduced risk as individuals grow and become too large to be consumed by gape-limited predatory fishes. Large-bodied species, such as sturgeon, may reach this size-refuge within the first year. However, there is limited understanding of what this size threshold is despite the value of this information for conservation management. We conducted laboratory-based predation experiments on juvenile green sturgeon, Acipenser medirostris, to estimate vulnerability to predation during outmigration from their natal reaches in California to the Pacific Ocean. Two highly abundant and non-native predatory fish species (largemouth bass, Micropterus salmoides, and striped bass, Morone saxatilis) were captured in the wild to be tested with developing juvenile green sturgeon from the UC Davis Green Sturgeon Broodstock Program. Experimental tanks, each containing five predators, received thirty prey for 24-hr exposures. Between sturgeon prey trials, predators were exposed to alternative prey species to confirm predators were exhibiting normal feeding behaviors. In addition to green sturgeon mortality data, trials were video recorded and predatory behaviors were quantified. Overall, these predator species displayed much lower rates of predation on juvenile green sturgeon than alternate prey. Predation decreased with green sturgeon size, and predation risk diminished to zero once sturgeon reached a length threshold of roughly 20–22 cm total length, or between 38% and 58% of predator total length. Behavioral analyses showed low motivation to feed on green sturgeon, with both predators attempting predation less frequently as sturgeon grew. Results of this study imply that optimizing growth rates for larval and juvenile sturgeon would shorten the time in which they are vulnerable to predation. Future experiments should assess predation risk of juvenile green sturgeon by additional predator species common to the Sacramento-San Joaquin watershed.     

Intraguild Interactions Between the Predatory Mites Neoseiulus californicus and Phytoseiulus persimilis

Species at the same trophic level may interact through competition for food, but can also interact through intraguild predation. Intraguild predation is widespread at the second and third trophic level and the effects may cascade down to the plant level. The effects of intraguild predation can be modified by antipredator behaviour in the intraguild prey. We studied intraguild predation and antipredator behaviour in two species of predatory mite, Neoseiulus californicus and Phytoseiulus persimilis, which are both used for control of the two-spotted spider mite in greenhouse and outdoor crops. Using a Y-tube olfactometer, we assessed in particular whether each of the two predators avoids odours emanating from prey patches occupied by the heterospecific predator. Furthermore, we measured the occurrence and rate of intraguild predation of different developmental stages of P. persimilis and N. californicus on bean leaves in absence or in presence of the shared prey. Neither of the two predator species avoided prey patches with the heterospecific competitor, both when inexperienced with the other predator and when experienced with prey patches occupied by the heterospecific predator. Intraguild experiments showed that N. californicus is a potential intraguild predator of P. persimilis. However, P. persimilis did not suffer much from intraguild predation as long as the shared prey was present. This is probably because N. californicus prefers to feed on two-spotted spider mites rather than on its intraguild prey.     

Sequential movement into coastal habitats and high spatial overlap of predator and prey suggest high predation pressure in protected areas

In theory, predators should attempt to match the distribution of their prey, and prey to avoid areas of high predation risk. However, there is a scarcity of empirical knowledge on predator and prey spatial use when both are moving freely in their natural environment. In the current study, we use information collated on a predators’ diet, its population structure, as well as predator and prey relative abundance, and track the movements of predator and prey simultaneously to compare habitat use and evaluate predation pressure. The study was conducted in elasmobranch protected areas of coastal Tasmania, Australia. The species considered were the broadnose sevengill shark Notorynchus cepedianus, the apex predator in the area, and five chondrichthyan prey species. Notorynchus cepedianus and its prey show similar seasonality in the use of these coastal areas: more abundant in warmer months and absent in winter. Predator and prey also showed high spatial overlap and similar habitat use patterns. These similar movement patterns of predator and prey combined with the additional ecological information (diet, population structure of predator, relative abundance of predator and prey) suggests that N. cepedianus move into coastal areas to exploit seasonally abundant prey. Also, while in protected areas, chondrichthyans are subjected to high predation pressure. Overall, results illustrate the value of simultaneously recording and integrating multiple types of information to explore predator–prey relationships and predation pressure.     

Direct and indirect effects of a predatory backswimmer (Notonecta maculata) on community structure of desert temporary pools

Abstract.

• 1 We assessed experimentally the effects of the predatory backswimmer, Notonecta maculata, on naturally colonizing mosquito populations in artificial outdoor pools in the Negev Desert, Israel. A single Notonecta adult per pool (8–15 litres water) had a very large negative impact on populations of Culiseta longiareolata, the most common species found in natural local pools. Notonecta caused large reductions of Culiseta egg rafts and early-instar larvae (instars I and II) and virtually 100% reductions of late-instar Culiseta larvae (instars III and IV) and pupae.
• 2 Notonecta also caused a trophic cascade in the experimental pools; by preying on periphyton-feeding Culiseta larvae, Notonecta indirectly caused significantly higher densities of diatoms, the major component of the periphyton.
• 3 Surveys of nearby natural pools taken between March and May supported the experimental results: a strong negative association between Notonecta and Culiseta among pools occurred as Notonecta increased in numbers and became more widely distributed. Anopheles (occurring only in May) and Culex mosquito immatures were not negatively associated with Notonecta. Culiseta was not associated with surface vegetation whereas both Culex and Anopheles showed strong positive associations with surface vegetation both among and within pools. We attribute the negative association between the predator and Culiseta to local prey extinctions caused by Notonecta in individual pools. Culiseta, being an open water species, is apparently more prone to predation by Notonecta than the vegetation-dwelling Culex and Anopheles.

     

人工微宇宙下粘细菌捕食对微生物群落结构的影响

【目的】人工微宇宙条件下测试粘细菌捕食对微生物群落结构的影响,模拟粘细菌捕食对微生态系统的调控作用。【方法】采用Lawn predation法,测定粘细菌EGB对9种猎物菌的捕食直径,以确定其对猎物菌的捕食能力。通过高通量测序技术分析粘细菌捕食引起的微生物群落结构变化。【结果】粘细菌EGB对9种不同猎物菌的捕食能力差异显著,粘细菌对热带芽孢杆菌的捕食能力显著高于其他细菌(P<0.05)。在含有9种猎物细菌的人工微宇宙系统中添加不等量粘细菌,均可显著降低细菌群落的多样性指数(Shannon)。PCoA结果表明粘细菌捕食可影响微宇宙微生物群落结构。人工微宇宙培养24 h后,7种猎物菌相对丰度显著降低(LefSe,P<0.05),但洋葱伯克霍尔德菌的相对丰度显著升高(P<0.05)。人工微宇宙实验的结果表明,粘细菌添加是造成其微生物群落结构改变的主要影响因素,且添加最小剂量的粘细菌(1 mL)也有显著的影响效果;随着培养时间的增加,洋葱伯克霍尔德菌是唯一能抵抗粘细菌捕食并具有较高丰度的猎物细菌。【结论】粘细菌捕食能够调控微宇宙中微生物的群落结构,为其对土壤生态的调控研究奠定了理论基础。     

Effect of adult females' predation risk on oviposition site selection in a water strider

In many egg‐laying species, females avoid ovipositing at sites where the predation risk is high. Previous studies have mainly focused on the risk for offspring. The effect of predation risk for the females has been considered in some taxa in which parents spend much time at an oviposition site for parental care or mating (e.g., birds, amphibians). In species in which females do not perform activities other than oviposition at sites, the effect of predation risk for females on oviposition site selection has been rarely investigated. We examined whether the predation risk for ovipositing females affects the decision on oviposition in the water strider Aquarius paludum insularis (Motschulsky) (Heteroptera: Gerridae). Adult A. paludum are preyed upon by a backswimmer, Notonecta triguttata (Motschulsky) (Heteroptera: Notonectidae), but N. triguttata does not prey upon eggs or early instars of A. paludum. We allowed female A. paludum to oviposit under one of three conditions: in presence of N. triguttata, in presence of its chemicals, and in absence of the predator or its cues (control). Female A. paludum less frequently oviposited in presence of N. triguttata than in its absence. Oviposition frequency did not differ between females in presence of chemicals of N. triguttata vs. those in the control. Female A. paludum recognized the predation risk upon themselves from the presence of N. triguttata and avoided ovipositing. This study is the first to directly show that the predation risk upon ovipositing females changes oviposition site selection in species in which the time spent at an oviposition site is short.     

Spatial Partitioning of Predation Risk in a Multiple Predator-Multiple Prey System

ABSTRACT Minimizing risk of predation from multiple predators can be difficult, particularly when the risk effects of one predator species may influence vulnerability to a second predator species. We decomposed spatial risk of predation in a 2-predator, 2-prey system into relative risk of encounter and, given an encounter, conditional relative risk of being killed. Then, we generated spatially explicit functions of total risk of predation for each prey species (elk [Cervus elaphus] and mule deer [Odocoileus hemionus]) by combining risks of encounter and kill. For both mule deer and elk, topographic and vegetation type effects, along with resource selection by their primary predator (cougars [Puma concolor] and wolves [Canis lupus], respectively), strongly influenced risk of encounter. Following an encounter, topographic and vegetation type effects altered the risk of predation for both ungulates. For mule deer, risk of direct predation was largely a function of cougar resource selection. However, for elk, risk of direct predation was not only a function of wolf occurrence, but also of habitat attributes that increased elk vulnerability to predation following an encounter. Our analysis of stage-based (i.e., encounter and kill) predation indicates that the risk effect of elk shifting to structurally complex habitat may ameliorate risk of direct predation by wolves but exacerbate risk of direct predation by cougars. Information on spatiotemporal patterns of predation will be become increasingly important as state agencies in the western United States face pressure to integrate predator and prey management.     

Effects of opportunistic predation on anti-predator behavioural responses in a guild of ground foragers

We studied factors that affect prey selection by a generalist predator that opportunistically attacks prey species, and the associated inter- and intra-specific responses of prey to this type of predation. Our model system was a guild of ground-foraging birds that are preyed upon by magpies (Pica pica) during the breeding season. We found that magpies attacked up to 12 species during three consecutive breeding seasons. The overall capture success was estimated to be 4.9%. Magpies tended to attack from the air, targeting solitary prey, either on the ground or flying. Inter-specific prey responses to the risk of magpie predation included a reduction in the mean number of species occupying a foraging patch when magpies were present and a decrease in the distance between heterospecific neighbours. Intra-specific responses to magpie predation varied between species that were subject to different attack rates. Preferentially attacked prey enhanced their risk responses (increase in scanning time and scanning rate in the presence of magpies) relative to those species attacked in proportion to their abundance (increase only in scanning rate with magpies). Species attacked infrequently, relative to their abundance, showed no antipredator response. The probability of being attacked, rather than mortality rate, appears to be the factor to which prey species respond.     

Behavioural responses to predation may explain shifts in community structure

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Predation Risk Avoidance by Terrestrial Amphibians: The Role of Prey Experience and Vulnerability to Native and Exotic Predators

We studied avoidance, by four amphibian prey species (Rana luteiventris, Ambystoma macrodactylum, Pseudacris regilla, Tarichia granulosa), of chemical cues associated with native garter snake (Thamnophis elegans) or exotic bullfrog (R. catesbeiana) predators. We predicted that avoidance of native predators would be most pronounced, and that prey species would differ in the intensity of their avoidance based on relative levels of vulnerability to predators in the wild. Adult R. luteiventris (presumably high vulnerability to predation) showed significant avoidance of chemical cues from both predators, A. macrodactylum (intermediate vulnerability to predation) avoided T. elegans only, while P. regilla (intermediate vulnerability to predation) and T. granulosa (low vulnerability to predation) showed no avoidance of either predator. We assessed if predator avoidance was innate and/or learned by testing responses of prey having disparate levels of prior exposure to predators. Wild‐caught (presumably predator‐exposed) post‐metamorphic juvenile R. luteiventris and P. regilla avoided T. elegans cues, while laboratory‐reared (predator‐naive) conspecifics did not; prior exposure to R. catesbeiana was not related to behavioural avoidance among adult or post‐metamorphic juvenile wild‐reared A. macrodactylum and P. regilla. These results imply that (i) some but not all species of amphibian prey avoid perceived risk from garter snake and bullfrog predators, (ii) the magnitude of this response probably differs according to prey vulnerability to predation in the wild, and (iii) avoidance tends to be largely learned rather than innate. Yet, the limited prevalence and intensity of amphibian responses to predation risk observed herein may be indicative of either a relatively weak predator–prey relationship and/or the limited importance of predator chemical cues in this particular system.     

Effects of predator density and duration of predator occupancy on crustacean abundance and diversity in experimental pools

Keystone predators, by reducing the abundance of competitively superior prey, may have indirect positive effects on weak competitors, possibly increasing their abundance or preventing local competitive exclusion. By analogy to the Intermediate Disturbance Hypothesis, we would expect species diversity to peak at intermediate predator densities. In a replicated artificial pool experiment, we examined the relationships between density of the backswimmer Notonecta maculata (0, 1, 2, and 4 per 30 l pool) and invertebrate taxon diversity over an 11-week period of predator occupancy. Diversity reached high levels at high predator density sooner than at intermediate density. At the end of the experiment, taxon diversity was greatest at densities of 2 and 4 Notonecta per pool. While the overall predator density–diversity curve was in line with the intermediate disturbance hypothesis, the reduction in diversity from intermediate to high predator density was not statistically significant. Density of the preferred prey Daphnia magna decreased with Notonecta density, while densities of the smaller cladocerans Moina brachiata and Ceriodaphnia spp. increased. Suppression of Daphnia at high Notonecta densities may partially explain the increase in Moina and Ceriodaphnia densities. However, most of the relationship between Notonecta and the smaller cladocerans appears to be independent of Daphnia, suggesting complex interactions within the community. Our results suggest that keystone predation plays a strong role in structuring this community. Although diversity did not decrease significantly at the highest predator density as predicted, such a decrease may be more likely for pools with longer durations of predator occupancy or with higher predator densities.     

Impact of predation on early stages of the armoured catfish Hoplosternum thoracatum (Siluriformes-Callichthyidae) and implications for the syntopic occurrence with other related catfishes in a neotropical multi-predator swamp

This study investigated the role of predators in preventing competitive exclusion among three closely related armoured catfishes (Callichthys callichthys, Hoplosternum littorale and H. thoracatum) that occur synthopically in multi-predator freshwater swamps of Suriname, South America. The potential impact of predation on armoured catfish was determined by combining laboratory measurements of predation rates on five early developmental stages of the armoured catfish H. thoracatum for 24 aquatic predators with field studies of the density of the predators in the swamps. The contribution of a particular predator to the total predation pressure on its prey was determined to a large extent by the density of the predator in the swamp. Seemingly innocuous predators with low or moderate predation rates in the laboratory may be extremely important in the swamps due to their high abundance. Small-sized omnivorous fishes and aquatic invertebrates were major predators of early developmental stages of armoured catfish. Both qualitative and quantitative ontogenetic changes in the predation pressure on armoured catfish were observed. Major predation on eggs, larvae and juveniles of H. thoracatum resulted from a different set of predators in each developmental stage of the prey. In all developmental stages of H. thoracatum the predation pressure involved several predator species and not a single, dominant predator. The potential predation pressure of the 24 predators taken together and the number of predators that were able to prey on H. thoracatum decreased sharply with increasing age (size) of the prey. Even if egg (nest) predation is prevented by the guarding male, the potential impact of the 24 predators on the populations of armoured catfish is large. Predation may account for the high mortality of H. thoracatum observed in the swamps. The high predation pressure on callichthyid catfishes may help to explain the coexistence of three closely related and morphologically quite similar armoured catfishes in Surinamese swamps.     

Is prey predation risk influenced more by increasing predator density or predator species richness in stream enclosures?

The direct lethal impacts and the indirect effects predators have on prey characteristics, such as behavior, have fitness consequences for the prey. Whether the level of predation risk that prey face in the presence of multiple predator species can be predicted from a null model that sums the risk from each predator species in isolation is unclear. In field enclosures, we tested whether the predation risk experienced by Stenonema mayfly larvae from a dragonfly larva (Boyeria vinosa) and a hellgrammite (Corydalus cornutus) together matched the predictions of the multiplicative risk model. We then compared whether any deviations from the models predictions were larger in the presence of two predator species than in the presence of an equivalent density of individuals from either predator species alone, to determine if unique effects arise for the prey in the presence of multiple predator species. We also determined if prey moved preferentially into predator-free refuge spaces or decreased their movement in the presence of predators. Stenonemas risk of predation was reduced compared to the models prediction, but no unique multiple predator species effects were present because this risk reduction was comparable in magnitude to the level exhibited in the presence of each predator species alone. The prey did not move into predator-free refuge spaces in the presence of predators in the field enclosures. Thus, these predators appear to interfere interspecifically and intraspecifically, which may facilitate the coexistence of the predators and the prey.